1. Field of the Invention
The invention relates to a plate changing device, and more particularly, to such a device having a roller disposed parallel to the plate cylinder and pressable against the plate cylinder by a positioning element, a rear or trailing edge of a printing plate being insertable thereby into a plate clamping or lock-up device.
2. Description of Related Art Including Information Disclosed Under Sections 1.97-1.99
Clamping or locking-up a printing plate on a plate cylinder of a printing machine has heretofore been an operation performed manually by a pressman. Devices for gripping or clamping the printing plate which received therein the front or locking and the rear or trailing edges of the printing plate and which could be opened and closed with a key or a gudgeon were provided for the foregoing purpose. The printing plate was inserted into such devices by hand.
The first advancement in this field was a development of devices for gripping or clamping printing plates which can be opened and closed by pushbutton pressure. By means of these devices, the printing plate is automatically gripped or clamped and subsequently tightened at the front or leading and the rear or trailing edges thereof. The front edge of the printing plate is insertable into the gripping or clamping device by hand, semiautomatically or fully automatically. To insert the rear or trailing edge of the printing plate, a device of the type described at the introduction hereto is required.
Such a device has become known heretofore from Japanese Patent Sho 63-191636. The insertion of the bent rear edge of a printing plate into the gripping, clamping or lock-up device of a printing cylinder is effected in the device of this Japanese patent, by a roller, which is supported on swivelable levers connected to a shaft. Provision is made, in the Japanese patent, for the roller to press the front edge of the printing plate to the surface of the plate cylinder after the front edge of the plate has been locked in place, so that then the rear edge of the printing plate, at the other end of the printing plate, can be inserted into the gripping, clamping or lock-up device of the plate cylinder. During this process, the shaft with the levers and the roller is displaced on a guide rail extending tangentially to the plate cylinder. The roller is pressed against the plate cylinder by means of a cylinder which actuates a rod connected to the levers.
This heretofore known device of the Japanese patent is of complex construction. It has many parts and requires a great amount of construction space, which is undesirable for the relatively narrow space conditions already existing between the printing units. Because of the relatively large amount of space required by the device of the Japanese patent, it is difficult to combine that device with a semiautomatic or fully automatic printing plate feeder. Advancements in automation require such a combination, however, and for reasons of economy, a combination of standardized elements is desirable. Not only the roller, but the shaft, as well, are located directly in front of the printing unit, which should be accessible at all times, for example, if a hickey has to be removed from the printing plate, or if the pressman, for some reason, must manually intervene. The device of the Japanese patent is also unable to be removed in a simple manner in order to gain better access to the printing unit.